PROLEGOMENA TOANYFUTUREMETAPHYSICS 807
which the synthetical unity of the perceptions is represented as necessary and uni-
versally valid.*
§ 23. Judgments, when considered merely as the condition of the union of given
representations in a consciousness, are rules. These rules, so far as they represent the
union as necessary, are rules a priori,and, insofar as they cannot be deduced from higher
rules, are principles. But in regard to the possibility of all experience, merely in relation
to the form of thinking in it, no conditions of judgments of experience are higher than
those which bring the appearances, according to the various form of their intuition, under
pure concepts of the understanding, which render the empirical judgment objectively
valid. These are therefore the a prioriprinciples of possible experience.
The principles of possible experience are then at the same time universal laws of
nature, which can be known a priori.And thus the problem of our second question,
“How is the pure science of nature possible?” is solved. For the system which is
required for the form of a science is to be met with in perfection here, because, beyond
the above-mentioned formal conditions of all judgments in general (and hence of all
rules in general) offered in logic, no others are possible, and these constitute a logical
system. The concepts grounded thereupon, which contain the a prioriconditions of all
synthetical and necessary judgments, accordingly constitute a transcendental system.
Finally the principles, by means of which all phenomena are subsumed under these
concepts, constitute a physical system, that is, a system of nature, which precedes all
empirical knowledge of nature, and makes it possible. It may in strictness be denomi-
nated the universal and pure science of nature.
§ 24. The first of the physical principles subsumes all phenomena, as intuitions in
space and time, under the concept of quantity, and is thus a principle of the application of
mathematics to experience. The second one subsumes the strictly empirical element,
namely, sensation, which denotes the real in intuitions, not indeed directly under the
concept of quantity, because sensation is not an intuition that containseither space or
time, though it places the respective object corresponding to it in both. But still there is
between reality (sense-representation) and the zero, or total void of intuition in time, a
difference which has a quantity. For between every given degree of light and of darkness,
between every degree of heat and of absolute cold, between every degree of weight and of
absolute lightness, between every degree of occupancy space and of totally void space,
diminishing degrees can be conceived, in the same manner as between consciousness and
total unconsciousness (psychological darkness) ever-diminishing degrees obtain. Hence
there is no perception that can prove an absolute absence; for instance, no psychological
darkness that cannot be considered as consciousness which is only outbalanced by a
stronger consciousness. This occurs in all cases of sensation, and so the understanding can
anticipate even sensations, which constitute the peculiar quality of empirical representations307306*But how does the proposition that judgments of experience contain necessity in the synthesis of
perceptions agree with my statement so often before inculcated that experience as cognition a posteriorican
afford contingent judgments only? When I say that experience teaches me something, I mean only the
perception that lies in experience—for example, that heat always follows the shining of the sun on a stone;
consequently the proposition of experience is always so far accidental. That this heat necessarily follows the
shining of the sun is contained indeed in the judgment of experience (by means of the concept of cause), yet
is a fact not learned by experience; for conversely, experience is first of all generated by this addition of the
concept of the understanding (of cause) to perception. How perception attains this addition may be seen by
referring in the Critiqueitself to the [first] section of the “Transcendental Faculty of Judgment.”